An RSF Component (e.g. UIInput, UILink) is said to peer with a tag in the markup which shares the same rsf:id. For example a component produced like

  UIInput.make(form, "category-name", "#{category.name}");

could peer with a tag in the markup written like

<input rsf:id="category-name" size="30" type="text" value="Snacks" /> 

The term "peering" is taken from the good old days of Sun's AWT windowing toolkit for Java, where operating-system-side native components were said to "peer with" Java-side representations such as java.awt.Button. The "pairing up" of a Java-side RSF primitive component together with a "native-side" markup tag by RSF's IKAT renderer is conceptually very similar.

Sun has considered AWT at EOL as of 1999, but you can't keep a good idea down. Eclipse's SWT, much more performant and usable than Sun's Swing makes use of native components once again in a "peering" type arrangment, although with a much better division of labour than in AWT. An analogy that has sometimes been made is that RSF's relation to JSF is comparable to AWT's relation to Swing.